CHEMICAL SCIENCE

Nickel catalysts cost-effectively prepare polyketone polymer materials


On May 16, 2022, The team of Professor Liu Ye of the State Key Laboratory of Fine Chemicals of Dalian University of Technology held a meeting at Angew. Chem. Int. A new study titled “Cationic P, O-Coordinated Nickel(II) Catalysts for Carbonylative Polymerization of Ethylene: Unexpected Productivity via Subtle Electronic Variation” was published.

Based on the ligand electron regulation strategy, the research group developed a phosphine-phosphamide (PNPO) type cationic nickel catalytic system, successfully applied it to the ethylene carbonylation polymerization reaction, and finally prepared a polyketone material with completely alternating structure. The first author of the paper is Chen Shiyu, a doctoral student at the School of Chemical Engineering of Dalian University of Technology, and the corresponding author is Professor Liu Ye.

Polyketone (PK) prepared by direct carbonylation polymerization of ethylene monomer is a new type of semi-crystalline thermoplastic engineering material with many excellent properties, such as impact resistance, resistance to organic solvents and high barrier properties, and is widely used in aerospace, automotive and textile fibers. As early as the 90s, this reaction was industrialized in shell, and into the 21st century, South Korea’s HYOSUNG company developed various grades of polyketone products, which are a widely used polymer material. Compared with nylon, polyketone is 3 times stronger in impact resistance, 1.4 to 2.5 times stronger in its stability to chemicals, and it is more than 14 times harder than polyacetal (POM), the hardest material available today. At present, most of the industrial preparation of polyketone materials use expensive metal palladium complexes, and for cheaper metal-nickel catalytic systems, research is very limited, mainly because the highly electrophilic nickel metal center is particularly susceptible to monomer poisoning, resulting in the reaction activity of nickel catalysts and the conversion of polyketones obtained are far lower than the palladium catalytic system, and the temperature and use pressure requirements are high, therefore, the development of simple, efficient and stable nickel catalytic systems is very promising for industrial applications, but there are also huge challenges.

Recently, Professor Liu Ye of the State Key Laboratory of Fine Chemicals of Dalian University of Technology built on the basis of the previous work (Chen Changle, Liu Ye. J. Am. Chem. Soc. 2021, 143, 10743−10750), based on the ligand electron regulation strategy, developed a phosphine-phosphamide (PNPO) type cationic nickel catalytic system, successfully applied to the ethylene carbonylation polymerization reaction, and prepared a completely alternating polyketone material by investigating the electron effect of the catalyst substituent, the pressure of the mixture and the temperature. It was found that the introduction of strongly electrified substituents at both the aromatic and phosphonic ends of the ligand backbone can effectively increase the reactivity, and the conversion of polyketones is as high as 31150 g (g Ni)-1, which is the same as the patented palladium industrial catalyst. In particular, the copolymerization reaction can be carried out at low pressure (1.0 MPa), which is conducive to improving the stability of the nickel catalyst, and by extending the reaction time, the polyketone yield can be obtained at a basically equivalent rate under high pressure. It is worth mentioning that this polyketone polymer has a molecular weight of millions (Mn = 1470 kg/mol) and a narrow distribution (Ð< 1.4), which can be expected to be used in the field of ultra-strong fibers. In addition, the report uses a nickel catalyst to achieve ethylene/propylene ternary carbonylation polymerization, and the 4.0% propylene insertion reduces the melting point of polyketones to 230 °C, effectively broadening the processing window of the material and improving its solubility, which is comparable to the commercialized polyketone performance.

Reviewers gave a very positive review of the work, with one reviewer stating that “The authors report a highly interesting finding involving a real breakthrough in CO/alkene co-polymerization (and perhaps in polymer science in general). Ultimately, this finding may indeed allow significantly more economic production of polyketones as engineering plastics and super strong fibers….” “The authors report a very interesting discovery, a real breakthrough in CO/olefin copolymerization (perhaps in the field of polymer science), which will ultimately promote the economic production of polyketones as engineering plastics and superfibers.” Therefore, the article was selected as VIP (TOP5%).

The project is supported by the National Natural Science Foundation of China (NSFC, Grants 22071016). (Source: Science Network)

Related paper information:https://doi.org/10.1002/anie.202204126



Source link

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button